Tesamorelin vs Sermorelin: Two GHRH Analogues Compared

Tesamorelin and sermorelin both stimulate growth hormone release by activating the pituitary GHRH receptor, but they are built differently. Sermorelin is the native GHRH(1-29) fragment with a C-terminal amide, the shortest fully active piece of the hormone. Tesamorelin is the complete 44-residue GHRH with a trans-3-hexenoyl cap on its N-terminus. That cap, and the extra 15 residues, account for most of the practical differences.

For laboratory research use only. The compounds discussed are not approved for human or veterinary use and are not drugs, foods or cosmetics. This article summarises published research and is not medical advice.

Key points

Same receptor (GHRH-R), same first 29 residues.
Sermorelin: unmodified 1–29 amide, 3357.9 g/mol. Tesamorelin: modified 1–44, ~5136 g/mol.
Tesamorelin’s N-terminal cap protects against DPP-4 cleavage; sermorelin has no such protection.
Clinical history: sermorelin mainly in paediatric GH deficiency (1980s–1990s); tesamorelin in HIV-associated abdominal fat (phase 3, 2000s).
Both contain Met27, an oxidation-prone residue.

Side-by-side comparison

	Sermorelin	Tesamorelin
Sequence	GHRH(1-29)-NH₂	trans-3-hexenoyl-GHRH(1-44)-NH₂
Formula / mass	C₁₄₉H₂₄₆N₄₄O₄₂S, 3357.9 g/mol	C₂₂₁H₃₆₆N₇₂O₆₇S, ~5136 g/mol
Protection from DPP-4	None	N-terminal hexenoyl group
Duration of action	Short; early paediatric regimens used multiple daily administrations	Longer; once-daily in phase 3 trials
Main clinical evidence	Children with GH deficiency	HIV-associated abdominal fat accumulation
Detection (anti-doping)	Both covered by a validated LC-MS/MS method (Memdouh et al., 2021)

Both are available for research: tesamorelin and sermorelin acetate, each with lot-level HPLC and MS data.

Sermorelin’s clinical background

Sermorelin was studied mainly as an alternative to GH in children with GH deficiency of hypothalamic origin, that is, children whose pituitary could still respond to GHRH. In a six-month randomised study of 43 prepubertal children, GHRH(1-29)-NH₂ was given subcutaneously three times daily at two dose levels and compared with daily GH. Height velocity increased in all but two children. It was lowest in the lower-dose GHRH group and comparable between the higher-dose GHRH and GH groups, but only GH increased height SDS for bone age (Neyzi et al., 1993). The need for multiple daily administrations reflects sermorelin’s short duration of action.

Tesamorelin’s clinical background

Tesamorelin’s phase 3 program targeted visceral fat in people with HIV on antiretroviral therapy. In the first 26-week trial (412 patients), visceral adipose tissue fell 15.2% with tesamorelin and rose 5.0% with placebo; IGF-I rose 81% (Falutz et al., 2007). Across two trials, effects were maintained with continued treatment to week 52 and reversed after stopping (Dhillon, 2011). See what is tesamorelin?

Stability and handling compared

Aspect	Sermorelin	Tesamorelin
Enzymatic stability (in vivo)	Low	Higher (N-terminal cap)
Oxidation risk	Met27	Met27
Deamidation risk	Asn8	Asn8 (plus additional residues in 30–44)
Dissolution	Readily water-soluble	Water-soluble; larger, allow extra swirling time
Storage	Powder −20 °C; solution 2–8 °C, dark; avoid freeze–thaw

For both, minimise headspace air and light to slow methionine oxidation, which shows as a +16 Da species by MS. Use the peptide reconstitution calculator and see storing reconstituted peptides.

Why the extra 15 residues?

Residues 1–29 contain everything needed for receptor activation, which is why sermorelin is fully active. The longer tesamorelin sequence is closer to the natural hormone. Combined with the N-terminal cap, it gives a molecule that survives longer in circulation while still binding the receptor in the native way. The price is size: at about 5.1 kDa, tesamorelin is harder to synthesise and purify than a 29-residue peptide, which is one reason the shorter analogues remain common research tools.

Where CJC-1295 fits

CJC-1295 is a third route to a longer-acting GHRH analogue: it keeps the 1–29 length but substitutes four residues (including Met27→Leu, removing the oxidation site), and the DAC version adds albumin binding. See CJC-1295 with vs without DAC.

Open questions

How do the two compare head-to-head on GH and IGF-I profiles under identical conditions? Direct comparisons are lacking.
How much does the 30–44 region of tesamorelin contribute to receptor activity beyond protection and pharmacokinetics?

Related research

Frequently asked questions

What is the difference between tesamorelin and sermorelin?

Both are GHRH-receptor agonists. Sermorelin is the native GHRH(1-29) fragment with a C-terminal amide. Tesamorelin is the full 44-residue GHRH with a trans-3-hexenoyl group on the N-terminus that protects it from enzymatic cleavage.

Is tesamorelin the same as sermorelin?

No. They share the GHRH(1-29) sequence, but tesamorelin is 15 residues longer and chemically modified, giving it greater resistance to degradation.

Which has more clinical data?

Tesamorelin has more recent phase 3 data, from trials in HIV-associated abdominal fat accumulation. Sermorelin’s clinical studies, mainly in children with GH deficiency, date largely from the late 1980s and 1990s.

Does sermorelin need to be refrigerated?

As research material, store lyophilized sermorelin at −20 °C long-term and reconstituted solutions at 2–8 °C. Its unmodified methionine at position 27 makes it susceptible to oxidation.

What are their molecular weights?

Sermorelin is about 3357.9 g/mol and tesamorelin about 5136 g/mol, according to PubChem.

References

Falutz J, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007. PMID: 18057338 https://pubmed.ncbi.nlm.nih.gov/18057338/
Dhillon S. Tesamorelin: a review of its use in the management of HIV-associated lipodystrophy. Drugs. 2011. PMID: 21668043 https://pubmed.ncbi.nlm.nih.gov/21668043/
Neyzi O, et al. Growth response to growth hormone-releasing hormone(1-29)-NH2 compared with growth hormone. Acta Paediatr Suppl. 1993. PMID: 8329826 https://pubmed.ncbi.nlm.nih.gov/8329826/
Memdouh S, et al. Advances in the detection of growth hormone releasing hormone synthetic analogs. Drug Test Anal. 2021. PMID: 34665524 https://pubmed.ncbi.nlm.nih.gov/34665524/
PubChem Compound Summary for CID 16132413, Sermorelin. National Center for Biotechnology Information. https://pubchem.ncbi.nlm.nih.gov/compound/16132413
PubChem Compound Summary for CID 16137828, Tesamorelin. National Center for Biotechnology Information. https://pubchem.ncbi.nlm.nih.gov/compound/16137828